Spectrum sharing communications system for monitoring available spectrum

Abstract

A mobile radio communications network is provided with a system for allocating one or more ranges of transmission frequency to the communications network, in order to prevent the network from interfering with received signals of an incumbent radio system. The allocating system may be provided with a device for receiving and monitoring information indicative of the presence and location of incumbent radio stations. A signal level monitoring system monitors signals transmitted from incumbent radio stations to determine the frequency and degree of RF isolation, with respect to a monitoring antenna of the monitoring system, of the stations. The monitoring system includes monitoring antennas, a spectrum analyzer, a device for controlling the spectrum analyzer, and a device for processing and correcting the data produced by the spectrum analyzer.

What is claimed is: 
     
       1. A mobile communuications network in which signals are transmitted and received between at least one base station and at least one user terminal over a common block of frequency spectrum that is shared with an incumbent radio system having a plurality of incumbent radio stations, said mobile communications network comprising: means for periodically measuring signal levels of signals falling within a plurality of frequency segments of said common block of frequency spectrum, said measuring means comprising:   monitoring antennas, said monitoring antennas collectively having plural polarizations and being arranged to have spatial diversity;   a spectrum analyzer coupled to said monitoring antennas for producing data representative of a signal level contained within at least one frequency band received by each of said antennas;   means for controlling said spectrum analyzer; and   means for processing information, including data produced by said spectrum analyzer, to produce data representative of a frequency of an incumbent receiver and a degree of RF isolation between at least one of said monitoring antennas and said incumbent receiver;   means for identifying which of said plurality of incumbent radio stations are nearby incumbent radio stations based on the signal levels measured by said measuring means;   means for calculating whether interference is likely to occur between said mobile communications network and at least one of the nearby incumbent radio stations identified by said identifying means;   means for periodically creating parameters, representative of the range of frequencies on which said user terminal transmits and receives said signals, based on a likelihood of interference calculated by said calculating means; and   means for periodically assigning frequencies on which said user terminal transmits and receives said signals based on the parameters created by said creating means.   
     
     
       2. The mobile communications network according to claim 1, wherein said processing means comprises: means for storing signal level data measured by each of said antennas, and for assigning one data record per antenna;   means for detecting bursts in said signal level data;   means for determining when abnormally high signal levels above a predetermined threshold value are measured;   means for re-measuring said signals, and adjusting said signal levels when a re-measurement of said signals results in a lower measured signal level which is below said predetermined threshold value;   means for integrating the signal level measured over a specified frequency range; and   means for correcting the measured signal level data in accordance with calibration data.   
     
     
       3. The mobile communications network according to claim 1, wherein said processing means comprises a system database which comprises parameters of an incumbent radio system, said information which is processed by said information processing means further comprising said parameters. 
     
     
       4. The mobile communications network according to claim 1, wherein said measuring means further comprises: means for measuring a signal level within a discrete frequency range; means for collecting a plurality of measured signals levels within the discrete frequency range; and means for averaging the collected signal level values corresponding to the discrete frequency range. 
     
     
       5. The mobile communications network according to claim 1, wherein said measuring means comprises: means for determining if the measured levels of signals contain intermodulation products generated within said network; and means for subtracting intermodulation products from measured signal level data. 
     
     
       6. The mobile communications network according to claim 1, wherein said measuring means further comprises: means for taking plural measurements; and means for determining which of the measurements indicates a least amount of RF isolation between said mobile communications network and an incumbent radio system transmitter. 
     
     
       7. The mobile communications network according to claim 1, further comprising a positioning system for detecting the position of said measuring means. 
     
     
       8. The mobile communications network according to claim 1, further comprising: means for comparing said signal level values with a predetermined threshold value;   means for identifying a transmitter of said incumbent radio system which corresponds to each signal level value which is determined to be above said threshold value;   means for identifying a receiver which is co-located with said transmitter; and   means for determining the frequency at which said receiver receives signals.   
     
     
       9. The mobile communications network according to claim 1, wherein said monitoring antennas comprise directional antennas. 
     
     
       10. The mobile communications network according to claim 1, wherein said monitoring antennas comprise antennas collectively having both horizontal and vertical polarizations. 
     
     
       11. The mobile communications network according to claim 1, wherein said monitoring antennas comprise a steerable array of antennas. 
     
     
       12. The mobile communications network according to claim 1, wherein said identifying means comprises: data storage means for storing information representing incumbent radio stations and the respective geographic locations of said incumbent radio stations; and   means for determining which incumbent radio stations have a geographic location within a predetermined range of a signal measurement location and have a transmit or receipt frequency that is within a predetermined range of said frequency segment.